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Author Topic: Eimac 4-1000A Typical Operating Specs for Grounded Grid Operation - rare  (Read 6961 times)
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K1JJ
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« on: February 11, 2009, 11:44:40 PM »

The 4X1 tetrode is an anomaly when placed in hi-mu GG triode service. It is cleaner than most other tetrodes in GG.  That's why the triode-connected 4X1 modulators work so well. Same for 813's.


Frank/GFZ sent me this engr letter from Eimac about 4X1 operating specs.  

It includes some good, hands-on  info.

GG  specs for tetrodes as triode configured are usually hard to come by.

Great -  the drive input impedance is 106 ohms per tube... higher than I thought.  A  pair wud make 53 ohms.

73,

Tom, K1JJ


* eimac- 4-1000A.jpg (262.76 KB, 600x795 - viewed 812 times.)
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« Reply #1 on: February 12, 2009, 09:51:16 AM »

Frank/GFZ sent me this engr letter from Eimac about 4X1 operating specs. 

It includes some good, hands-on  info.

GG  specs for tetrodes as triode configured are usually hard to come by.

Great -  the drive input impedance is 106 ohms per tube... higher than I thought.  A  pair wud make 53 ohms.

73,

Tom, K1JJ


You still need a flywheel for that.....

Simple pi net input and pi net output works GREAT on a pair of 1000s.


--Shane
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w5jai
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« Reply #2 on: March 01, 2009, 02:12:31 PM »

I recently acquired a pair of 4-1000A linears.  One uses two tubes and the other uses only one tube.  I also got the power supply with them.  Maybe someday I will try to sort out the schematic and try to get one of them on the air.  They are both brand new and have never been fired up as far as I can tell.  The big thing holding me back is needing three people to move the power supply!!!

I am currently working on a Multi-Elmac and I could use it as an AM exciter to push a pair 4-1000As.  That would put out an awesome signal.


* 4-1000 Linears #1.jpg (1649.54 KB, 3264x2448 - viewed 677 times.)

* 4-1000 Linears #2.jpg (1624.02 KB, 3264x2448 - viewed 647 times.)

* 4-1000 Linears #3.jpg (1614.74 KB, 3264x2448 - viewed 634 times.)
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K1JJ
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« Reply #3 on: March 01, 2009, 02:36:58 PM »

Hi Jim,

Very nice work, OM!

You use many of the same type parts I have used here.... even the turns counters made from that old fella in Ohio.. :-)

Can you post some shots of the pair of 4X1's too?

The 4X1's will make a beautiful amp for your AM driver. It will put you in the same power class as the common 1KW broadcash transmitters on the air today.  What voltage do you plan to use on them?

I like the air chimney for proper cooling - good going... :-)

Question:  Your plate coupling cap - I've never used that style of capacitor before for RF plate coupling, just by bypassing. Have you had experience with them in QRO service for RF coupling caps?   I've found that coupling caps take tremendous abuse and some will "sing" with audio and sometimes explode. (door-knobs for one) You might even consider mounting that one on ceramic stand-offs to be sure of the cap's mount RF break-down insulation.


**  BTW, before you fire it up....  It's hard to tell by the pics, but are you grounding the END of the variable caps and putting RF on the front near the shaft?  Think that out carefully, cuz you don't want RF HV coming down that shaft on C1, the plate tuning cap. (or DC HV in case the coupling cap fails)  Those shaft couplers will not be enuff isolation for total safety.  The variable cap is designed to have the HV on the end and the ground at the shaft end.   Give it some extra thought to be sure - but if I have interpreted the layout incorrectly, then please delete this paragraph ...   Cheesy


Thanks for posting the pics. They certainly help to inspire others to build up their own stuff.


73,

Tom, K1JJ
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« Reply #4 on: March 01, 2009, 02:55:15 PM »

Very clean layout on those. The plate inductor almost looks like a suplus sales of nebraska unit.
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w5jai
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« Reply #5 on: March 01, 2009, 05:53:31 PM »

Here are three more pictures.  I retrieved these from storage in a barn where they had been stored by the previous owner, the builder.  They were never fired up and I have not yet traced out the schematics on them so don't know the details.  As you can see the dual 4-1000A unit needs some cleaning, but its not as bad as it looks in the pictures.  I think there were some chickens roosting in the barn, but luckily they didnt use the linears for a toilet. Shocked

The power supply is a 6000 volt supply and I have the parts for another 5000 volt supply. Smiley


* 4-1000 Linears #6.jpg (1586.8 KB, 3264x2448 - viewed 475 times.)

* 4-1000 Linears #7.jpg (1543.61 KB, 3264x2448 - viewed 409 times.)

* 4-1000 Linears #8.jpg (1600.8 KB, 3264x2448 - viewed 359 times.)
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WA1GFZ
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« Reply #6 on: March 01, 2009, 06:03:54 PM »

The single amp is very nice but I agree with Tom, ground the shaft end of the plate tune cap and get a better plate blocking cap. That insulated shaft coupling WILL NOT CUT IT. You want nice short direct leads first to the plate tuning cap then to the inductor. Going to the inductor first with a stub to the cap could set up a VHF oscillation.
The dual amp I would get a smaller plate blocker so it will have shorter leads.
The metal work is beautiful!
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w5jai
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« Reply #7 on: March 01, 2009, 06:35:54 PM »

I havent even looked closely at them.  I aquired them about a year ago from a friend who got them from an SKs widow.  I have so many projects on line now and only about 50 more years to finish them.  But since I am now working on the AF-67 setup it looked like one of these might make a nice addition to that project.  I have all the tubes and chimneys so getting one on the air would not be expensive, just labor intensive.  Both of them have the same front panel and only by looking inside can you see the differences.
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« Reply #8 on: March 01, 2009, 08:29:16 PM »

the stuf that turns up is amazing..
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« Reply #9 on: March 01, 2009, 09:32:16 PM »

all the hard work is done. The suggested mods can be installed in a couple hours. hopefully the heater transformers are under the deck. That daul amp with about 50 to 75 watts of carrier will really rock.
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w5jai
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« Reply #10 on: March 01, 2009, 11:56:40 PM »

The filament transformers are in the power supply which is a large desk with power connectors and blowers that connect to the bottom of the amp chassis.
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K1JJ
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« Reply #11 on: March 02, 2009, 12:22:00 AM »

The filament transformers are in the power supply which is a large desk with power connectors and blowers that connect to the bottom of the amp chassis.

Sounds like a great start, Jim.

Many of us would love to come across well built, "almost finished" rigs like that. They are more desireable than commercial gear - at least to me.

Good luck wid it, OM.

T
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December / 1964    to    December/ 2014 will mark 50 years in this hobby.   Yikes!  Brrrrrrr.

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« Reply #12 on: March 02, 2009, 11:34:20 AM »

I hope those filament V connectors are at least the large Jones type with paralled contacts ... maybe some welding type ... curious ... this is not too easy to do without some voltage drop ...73 ..John
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Beefus
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« Reply #13 on: March 02, 2009, 07:21:40 PM »

I'd move them into the RF deck.
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« Reply #14 on: March 02, 2009, 07:42:27 PM »

rodney Rodney
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Beefus
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« Reply #15 on: March 02, 2009, 07:50:13 PM »

Thanks for posting the pictures....both amps are well built.....I noticed the use of pop rivets in the chassis...If the chassis sections that are pop riveted to each other carry the chassis ground I would advise at least one bolt between the sections to assure good bonding...
  On the tube sockets where the tube pins fit...What is the on the pinholders? It looks like some sort of sleeve.... I have not used any 4x1 sockets other than the eimac air type so I havent seen this before.  Good luck ..That two holer is great...  Steve   
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w5jai
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« Reply #16 on: March 03, 2009, 05:58:05 PM »

I almost wish I hadnt seen this thread.  It got me back into this pile of stuff that I had stored at the back of the garage.  When I bought the pile I just brought the whole stack to the garage and pushed it to the back.  Now I am beginning to see what I got for my $125.

Attached are pictures I took this afternoon of the two power supplys that came with these linears.  The one in the wood case is for the dual 4-1000A linear and the other is for the single 4-1000A linear.  Both are 5000Volts.  The one for the single 4-1000A does not have a plate voltage meeter so depends on the meter in the front panel of the Linear.

The larger one has the filament supply on the right and the plate supply on the left.  As you can see, it would not fit in the bottom of the linear!!!

Now, yes, the work to be done on the linears is small, less than a days work including the cleaning.  BUT...I think those power supplys may soak up a week to get them all sorted out!!!


* Linear Power Supply #1.jpg (1622.72 KB, 3264x2448 - viewed 310 times.)

* Linear Power Supply #2.jpg (1589.85 KB, 3264x2448 - viewed 229 times.)
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Steve - WB3HUZ
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« Reply #17 on: March 03, 2009, 06:58:15 PM »

What you got for $125 for a VERY good deal!  Grin
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WA1GFZ
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« Reply #18 on: March 03, 2009, 07:30:16 PM »

4-1000As kick butt at 5KW but the layout needs to be perfect to tame them.
I suggest you get a variac and work your way up. Make sure you have some bias on the tubes at that voltage. I was making 1700 watts with a single tube on 10 meters with that kind of voltage. My efficiency on 10 was only 55% so you can imagine how well you can do on 75. You will need plenty of air. I didn't have quite enough air on mine at that power. You could almost see through the plate when it glows yellow.
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w5jai
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« Reply #19 on: March 03, 2009, 09:26:11 PM »

ALL the supplies are on Variacs. Grin  Note the 4 knobs on the panels.  These are variacs that can be adjusted to get the B+ and Heater values to the desired level.
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w5jai
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« Reply #20 on: March 03, 2009, 09:37:17 PM »

What you got for $125 for a VERY good deal!  Grin

Yes, I paid that price for the three 4-1000As and the chimneys.  I figured they were easily worth that.  The rest was gravy.
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K1JJ
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« Reply #21 on: March 03, 2009, 09:45:01 PM »

What you got for $125 for a VERY good deal!  Grin

Yes, I paid that price for the three 4-1000As and the chimneys.  I figured they were easily worth that.  The rest was gravy.


You're making me feel bad. I just paid $90 each for two good 4X1's (one 4PR-1000A) and thought I made out... :-)
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December / 1964    to    December/ 2014 will mark 50 years in this hobby.   Yikes!  Brrrrrrr.

Come to my seminar!
https://www.youtube.com/watch?v=kzsSpDyBc_4

https://www.youtube.com/watch?v=jYqDS9i8zJw&index=2&list=PL6CF7E76DA0457573
N3DRB The Derb
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« Reply #22 on: March 03, 2009, 10:03:53 PM »

while you're at it, clean up supply for #1, quick fix the finish with howards and spray it with some deft semi gloss lacquer! How cool is a shiny wood cabinet for ur 4X1?
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Steve - WB3HUZ
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« Reply #23 on: March 03, 2009, 10:06:02 PM »

What you got.... is a thing.... a whole series of things... it's gonna wipe  out the moon walk!
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w5jai
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« Reply #24 on: March 03, 2009, 10:15:41 PM »

That sounds really spooky.  Maybe I better throw the tarp back over it and go back to my AF-67..... Shocked
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